just as an FYI, the KoV2 cart in the guide for the Ketsui conversion is a Nine Dragons cart, not a vanilla KoV2, and you can tell by the white silkscreened traditional chinese text below U8. also, apocalypse mentioned the ROMS don't match up in MAME, but they absolutely do for Nine Dragons (it's KoV2 Plus in MAME). also, you can pull 3.3v from the 29L33 (U19 on the board in the guide), so probably not necessary to buy additional parts. on my KoV2 cart it's a uPC29L33, and I verified by measuring 3.3v on the output pin.
all of that said, if anyone has info on converting a vanilla KoV2 I'd be interested. the process is definitely not the same to Nine Dragons.
The DoDonPachi conversion worked perfect and was quite easy to do. I also used the onboard voltage regulator for that conversion and it seems to work fine. Not sure if the VR is up to the task of feeding all the 3.3V roms over time though.